Editing Return loss (section)

==Electrical==
In metallic conductor systems, reflections of a [[signal]] traveling down a conductor can occur at a discontinuity or [[Electrical impedance|impedance]] mismatch. The ratio
: <math>\Gamma = \frac{V_\text{r}}{V_\text{i}}</math>
of the amplitude of the reflected wave ''V''<sub>r</sub> to the amplitude of the incident wave ''V''<sub>i</sub> is known as the [[reflection coefficient]].

Return loss is the negative of the magnitude of the reflection coefficient in dB. Since power is proportional to the square of the voltage, return loss is given by
: <math>\text{RL}(\text{dB}) = -20 \log_{10} |\Gamma|,</math>
where the [[vertical direction|vertical]] bars indicate [[magnitude (mathematics)|magnitude]]. Thus, a large positive return loss indicates that the reflected power is small relative to the incident power, which indicates good impedance match between transmission line and load.

If the incident power and the reflected power are expressed in "absolute" [[decibel]] units, (e.g., [[dBm]]), then the return loss in dB can be calculated as the difference between the incident power ''P''<sub>i</sub> (in absolute [[dBm]] units) and the reflected power ''P''<sub>r</sub> (also in absolute [[dBm]] units):
: <math>\text{RL}(\text{dB}) = P_\text{i}(\text{dBm}) - P_\text{r}(\text{dBm}).</math>